• Water for future
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• v.29 no.1
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• pp.141-150
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• 1996

Steady state analysis of pressure and flow in water supply piping systems is a problem of great importance in hydraulic engineering. The basic equations consist of continuity equation and energy equation. The network equations are solved iteratively by using linear solution method. The resulting linear simultaneous equations are solved by frontal method. Frontal method, which is suitable to sparse matrix, gathers only non-zero entries in coefficient matrix. The suggested methodology can analyze faster than the existing routines by using smaller computer memory. The model presented in this study shows accurate and efficient results for various piping systems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.838-843
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• 2005

The nonlinear characteristics of a suspension is directly related to the ride quality of a passenger car. In this study, a dynamic experiment for a spring and a damper of a passenger car is performed to analyze the nonlinear characteristics using MTS 1-axial testing machine and a mathematical nonlinear dynamic suspension model based on experimental data is devised to estimate the ride quality using Billings' method. The devised nonlinear model is applied to the ride quality analysis using K factor and the effect of suspension parameters is examined. As a result, the friction between the cylinder and the piston of a damper is the most effective parameter for the ride quality of a passenger car.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.131-132
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• 2015

본 논문에서는 3상 계통형 컨버터의 비선형성을 제거하기 위한 전향보상 기법을 제안하였다. 기존 제어방식은 출력전압 지령을 램프함수 형태로 인가하는 기법을 사용하여 오버슈트 전압을 저감해 주었다. 또는 램프함수의 초기 시작점에 대한 오차를 보완하기 위해 옵셋을 램프함수 초기에 더해주어, 제어 시작 시 발생하는 약간의 리플 전류를 저감해주었다. 하지만 이러한 리플 전류의 근본적인 원인은 제어기의 시작이 0에서부터 증가하여 과변조가 발생하기 때문이다. 이로 인한 순간적으로 큰 리플 전류는 더 높은 정격의 커패시터를 필요로 하게 되고, 이는 커패시터의 크기, 가격을 높이며 뿐만 아니라 소자의 수명을 단축시키는 원인이 된다. 이러한 문제를 없애기 위해 제안하는 전향보상 기법을 적용하여 보다 선형적인 제어기를 구성하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1277-1284
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• 2015

In this paper, 1-axis tracking mechanism of solar-cell panel, which is able to rotate from -90 degree to +90 degree for maintaining always perpendicular between solar-cell panel and sun, was analyzed. This paper propose the non-linear shaped guidance and analyze mathematical formulation of non-linear shape. This analysis shows that it is able to identify the non-linear shaped guidance. Especially, even though the length of rotating link have changed, the non-linear shaped guidance could be confirm with proper size. As effectiveness of this result, 10% efficiency rising is estimated compared to the conventional 1-axis tracking mechanism and also optimal non-linear shaped guidance can be suggested for various size of solar-cell panel. Therefore the flexible mass-production is possible for various size of non-linear shaped guidance.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.159-179
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• 2006

By using the current road design method that is based on the regulation about structure and facilities standard of the road and the route plan guide of a national road and the alignment optimization road design method which is studied in the inside and outside of country, this study operate the route plan of the sample study and compare and analysis the route character, consequently the current design method has local optimization that is formed the plan by the stage and the section. Alignment optimization road design has the system optimal route search. But cost function has limite that caused by construction parameter that is not included in cost function. So we design a road route included cost function in main fields. As a result, we obtain a realistic and economically road route. The alignment optimization road design model has to be made up some problems, like the change of vertical gradient in the tunnel section, though this defects it has a lot of merits as a geometric design tool, especially in the feasibility study and the scheme design.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.447-452
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• 2005

기존의 단층 퍼셉트론은 출력 노드가 선형 분리 가능한 패턴들만을 분류할 수 있고 Exclusive OR와 같은 비선형 문제에 대해서는 분류할 수 없는 단점이 있다. 그러나 퍼지 단층 퍼셉트론은 퍼지소속 함수(fuzzy membership function)를 적용하여 단층 구조로 Exclusive OR 문제와 같은 고전적인 문제를 개선하였다. 그러나 퍼지 단층 퍼셉트론은 기존의 단층 퍼셉트론과 마찬가지로 결정 경계선이 진동하는 경우가 생기며 초기 가중치의 범위와 학습률에 따라 수렴성이 매우 낮아지는 단점이 있다. 따라서 본 논문에서는 바이어스항을 도입하여 결정 경계선이 진동하는 것을 방지하여 수렴성을 개선시키고 선형 활성화 함수를 제안하고 학습률과 모멘텀 개념을 도입하여 학습 시간을 단축시키는 개선된 퍼지 단층 퍼셉트론 알고리즘을 제안한다. 제안된 방법과 퍼지 단층 퍼셉트론간의 학습 성능을 분석하기 위하여 인공 신경망에서 벤치마크로 사용되는 exclusive OR 문제와 문자 패턴 분류에 적용하여 epoch 수와 수렴성을 비교한 결과, 제안된 방법이 기존의 퍼지 단층 퍼셉트론보다 학습 시간이 적게 소요되고 수렴성이 개선된 것을 확인하였다.

• Progress in Medical Physics
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• v.14 no.4
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• pp.240-248
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• 2003

The Monte Carlo calculation is the most accurate means of predicting radiation dose, but its accuracy is accompanied by an increase in the amount of time required to produce a statistically meaningful dose distribution. In this study, the effects on calculation time by introducing variance reduction techniques and increasing computing power, respectively, in the Monte Carlo dose calculation for a 6 MV photon beam from the Varian 600 C/D were estimated when maintaining accuracy of the Monte Carlo calculation results. The EGSnrc­based BEAMnrc code was used to simulate the beam and the EGSnrc­based DOSXYZnrc code to calculate dose distributions. Variance reduction techniques in the codes were used to describe reduced­physics, and a computer cluster consisting of ten PCs was built to execute parallel computing. As a result, time was more reduced by the use of variance reduction techniques than that by the increase of computing power. Because the use of the Monte Carlo dose calculation in clinical practice is yet limited by reducing the computational time only through improvements in computing power, introduction of reduced­physics into the Monte Carlo calculation is inevitable at this point. Therefore, a more active investigation of existing or new reduced­physics approaches is required.

• Korean Journal of Poultry Science
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• v.49 no.1
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• pp.15-23
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• 2022

We compared the degrees of vitality of 12 Korean native chicken breeds, such as Jaeraejong, Korean Rhode Island Red (Rhode), Korean White Leghorn, Korean Cornish (Cornish), and Korean Ogye breeds. The survival rate and telomere length were measured as vital markers. Telomere length was analyzed via quantitative fluorescence in situ hybridization method using the lymphocytes of 466 chickens. We found that the telomere length decreased linearly with increasing chronological age in all chicken breeds. Telomere length and telomere shortening rates (TSR) were significantly different among the chicken breeds after 20 weeks of age (P<0.01). Rhode had the longest telomere length and the lowest TSR, whereas Cornish had the shortest telomere length and the highest TSR. In terms of TSR, the telomere length of 50-week-old chickens was half of that of 8-week-old chickens. There was also a significant difference in survival rates among the breeds. Both Rhode and Korean Ogye had the highest survival rates, while Cornish had the lowest. There was a significant positive correlation between survival rate and telomere length, and telomere length in old age showed a higher correlation with survival rate than that in young age. Therefore, it is considered that TSR is more closely related to survival rate than the telomere length. Based on the telomere dynamics and survival rates of 12 Korean native chicken breeds, it was concluded that the Rhode breed and Cornish breed had the highest and lowest vitality, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1387-1393
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• 2007

Even if the linearly separable patterns can be classified by the conventional single layer perceptron, the non-linear problems such as XOR can not be classified by it. A fuzzy single layer perceptron can solve the conventional XOR problems by applying fuzzy membership functions. However, in the fuzzy single layer perception, there are a couple disadvantages which are a decision boundary is sometimes vibrating and a convergence may be extremely lowered according to the scopes of the initial values and learning rates. In this paper, for these reasons, we proposed an enhanced fuzzy single layer perceptron algorithm that can prevent from vibration the decision boundary by introducing a bias term and can also reduce the learn time by applying the modified delta rule which include the learning rates and the momentum concept and applying the new linear activation function. Consequently, the simulation results of the XOR and pattern classification problems presented that the proposed method provided the shorter learning time and better convergence than the conventional fuzzy single layer perceptron.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1233-1238
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• 2003

In this paper, radially corrugated circular-type microstrip patch antenna was devised and manufactured for GPS (center frequency: 1.575 GHz). Radially corrugated circular-type microstrip patch antenna having radiational corrugation-patch contributed to add size reduction ratio by lowering the resonant frequency because the edge current also has the extended and perpendicular path. As a result, radially corrugated circular-type microstrip patch antenna has 28 % area reduction than planer circular-type patch antenna for linear polarization and 27.7 % area reduction than planer circular-type patch antenna for circular polarization. Radially corrugated circular-type microstrip patch antenna is suitable for miniaturized receive antenna for GPS which has the characteristic of gain 2.1 dBd, axiai ratio 1.3 dB, 2 dB axial bandwidth 15 MHz(0.9 %).